Electrostatic Auroral Density Cavities

A model set of nonlinear electrostatic equations is analyzed critically; they have been presented earlier to study the short-scale auroral density cavities (SSADC) observed by Freja satellite. It is shown that electron inertial effect is not necessary to obtain solitary structure through electrostatic nonlinear equations. The ion streaming and direction of propagation of the structure seem to be the two parameters that can decide the width of the density cavity.     

Neurons induce the activation of microglial cells in vitro

Although microglial cells are well known to become activated in the pathological brain, mechanisms underlying the microglial activation are not fully understood. In the present study, with an aim to elucidate whether neurons are involved in the microglial activation, we compared the morphology and the superoxide anion (O2-)-generating activity of rat microglial cells in pure culture with those of cells cocultured with rat primary cortical neurons. Microglial cells in pure culture in serum-free Eagle's minimum essential medium on poly-L-lysine-coated coverslips displayed ramified morphology and suppressed activity of O2- generation. In contrast, microglial cells in neuron-microglia coculture under the same conditions as those for the pure culture displayed ameboid shape and upregulated activity of O2- generation. Electron microscopic observation revealed that microglial cells in coculture were more abundant in Golgi apparatus and secretory granules than those in pure culture and that some of microglial cells in the vicinity of neurites exhibited membrane specialization reminiscent of a junctional apparatus with high electron density between a microglial soma and a neurite. Microglial cells in coculture tended to tie neurites in bundles by extending processes. Medium conditioned by neurons significantly enhanced O2- generation by microglia, but microglial cells in contact with or in close apposition to cocultured neurons were much more intensely activated than those remote from the neurons. Furthermore, the membrane fraction of cortical neurons activated microglial cells, and this effect was abolished by treating the neuronal membrane with trypsin or neuraminidase. In conclusion, neuronal-microglial contact may be necessary to mediate microglial activation. The present findings suggest that the contact of microglia with damaged neurons in the brain is a plausible cause to activate microglia in the neuropathological processes.     

Growth of High-Quality Pb((Zn1/3Nb2/3)0.91Ti0.09)O3 Single Crystals by Excess ZnO Addition

A high-quality single crystal of Pb((Zn_1/3Nb_2/3)_0.91Ti_0.09)O₃ (PZNT 91/9), 40 mm in diameter and 20 mm in length, was successfully grown using the solution Bridgman method with a slight excess amount of ZnO. High-quality wafers were sliced from the light-brown single crystal. No PbO inclusions or opaque areas were observed in the transparent wafers. An array probe for echocardiography was constructed with the single-crystal wafer, and its superior performance was demonstrated.     

PERFORMANCE OF A PRESSURIZED TWO-STAGE FLUIDIZED GASIFICATION PROCESS FOR PRODUCTION OF LOW-BTU GAS FROM COAL CHAR

A two-stage pressurized fluidized-bed gasification process has been developed to produce low-heating value gases from coal char. The reactor was 0.075 m id. and 1.4 m long, and gasification experiments were conducted under pressures up to 790 kPa and at temperatures up to 1323 K. A partition disc was used to divide the fluidized bed into two stages, using the first stage as a partial combuster and gasifier and the second stage as a gasifier. The disc was designed to control compositions of coal char particles in both stages so that the heat required for the endothermic gasification reaction in the second stage can be provided by the heat of combustion in the first

For conditions examined here, the disc with an opening ratio of 40° was found to give optimum distribution of the char particles in both stages without ash agglomeration. It was also shown that all oxygen gas was completely consumed within the first stage

The heating value of the product gas increased with the char feed rale. However, there may be an oplimum Teed ratio of char and sand-particles since the higher char feed rate causes more frequent ash agglomeration as well as less carbon conversion     

Crystal Growth and Electrical Properties of Pb((Zn1/3Nb2/3)0.91Ti0.09)O3 Single Crystals Produced by Solution Bridgman Method

Piezoelectric Pb((Zn_1/3Nb_2/3)_0.91Ti_0.09)O₃ (PZNT 91/9) single crystals 40 mm in diameter were successfully grown from solution by the Bridgman method with a PbO flux. The crystals were grown in a platinum crucible heated to 1130°C. Growth rate was 0.35 mm/h. The obtained crystals were ~40 mm in diameter 20 mm in length and were a rust-brown color. The Curie temperature, T _C, ranged from 175° to 185°C, and the dielectric constant before poling at room temperature was 2000-8900 within a wafer. After electrical poling, specimens had electromechanical coupling coefficients in rectangular bar mode, k _33´, of 79%-88%, which were larger than for PZT ceramics ( k _33´ < 70%). These PZNT 91/9 single crystals grown by the Bridgman process satisfy the requirements for array-type transducers used in echocardiographic equipment. Results confirm that the Bridgman method is useful for mass-producing large crystals of PZNT 91/9.     

Morphological changes of capillaries in the rat soleus muscle following experimental tenotomy

We examined the structural changes of capillaries in the rat soleus muscle 4, 7, 14, and 35 days after experimental limb tenotomy. In the soleus muscles after tenotomy, muscle fibres degenerated and some of them were destroyed; the muscle did not seem to recover until the 35th day. On the 14th day, some small muscle fibres, probably regenerating muscle fibres, started forming within the basal-lamina tube and remained after necrosis of a pre-existing muscle fibre. Most capillaries at each stage were of the continuous type. However, about 10% of the capillaries around degenerated muscle fibres at days 4, 7 and 14 consisted of endothelial cells with a small number of fenestrae bridged by a single-layered diaphragm. On the 14th day, capillaries around small regenerating muscle fibres also often had a small number of fenestrations. Even on the 35th day, capillaries occasionally had fenestrations. Additionally, some of the fenestrated capillaries formed small pores at the fenestrated portion of the endothelial cells. The untreated muscles contained only continuous capillaries. These findings suggest that fenestrations in the endothelial cells may occur in intramuscular capillaries not only around degenerated muscle fibres but also around regenerating muscle fibres after tenotomy.     

Antimicrobial effects of green tea polyphenols on thermophilic spore-forming bacteria

The inhibitory action of tea polyphenols towards the development and growth of bacterial spores was examined. Among the tested Bacillus bacteria, tea polyphenols showed antibacterial effects towards Bacillus stearothermophilus, which is a thermophilic spore-forming bacterium. The heat resistance of B. stearothermophilus spores was reduced by the addition of tea polyphenols. Clostridium thermoaceticum, an anaerobic spore-forming bacterium, also exhibited reduced heat resistance of its spores in the presence of tea polyphenols. (-)-Epigallocatechin gallate, which is the main component of tea polyphenols, showed strong activity against both B. stearothermophilus and C. thermoaceticum. The heat resistance of these bacterial spores was more rapidly decreased by the addition of tea polyphenols at high temperatures.     

Protective effect of a prostaglandin I2 analog, TEI-7165, on ischemic neuronal damage in gerbils

In this study we have analyzed short- and long-term changes in extracellular signal-regulated kinase (ERK) 1 and 2 activity during 12-O-tetradecanoylphorbol 13-acetate (TPA)-induced differentiation of human promyelocytic leukemia cells. Immunoprecipitation of HL-60 cellular extracts with an ERK antibody followed by in vitro myelin basic protein phosphorylation demonstrated a rapid reduction in total ERK activity by 70%. Mitogen-activated protein kinase substrate peptide phosphorylation also demonstrated that this reduction was sustained during differentiation. Immunoblot analysis revealed that ERK1 and ERK2 are the predominant ERK isoforms present in HL-60 cells and that over a 96-h period ERK1 protein was gradually reduced by 60% while ERK2 protein showed only a small, insignificant reduction. Therefore, the large, rapid decrease in total ERK activity could not be attributed to the gradual reductions in ERK1 or ERK2 amounts. Immunoblot analysis with two different phosphotyrosine antibodies revealed a rapid decrease in ERK1 phosphotyrosine and a concurrent transient increase in ERK2 phosphotyrosine. These contrasting changes in phosphorylated ERKs were paralleled by respective shifts in mobility during SDS-PAGE analysis. Together these results indicate that the rapid reduction in total ERK activity is due to rapid tyrosine and possible threonine dephosphorylation of ERK1 but not of ERK2. These results also indicate that ERK1 and ERK2 are regulated by distinct mechanisms during TPA-induced HL-60 differentiation, suggesting that their biological roles are nonredundant.     

Disappearance of Maillard reaction products during ensilage and rumen fermentation in vitro

The disappearance of Maillard reaction products (MRPs) during ensilage and rumen fermentation was studied. MRPs were prepared by heating mixtures of D ‐glucose and glycine (GG) or D ‐xylose and glycine (XG); lyophilised powder (MW > 1000) was subjected to anaerobic incubation for 24 h with lucerne juice or buffered rumen fluid. Changes in MRPs were assessed by comparing gel filtration profiles before and after incubation, and the proportion of disappeared MRPs was calculated based on the area under the curve. A portion of MRPs, particularly high‐MW fractions, disappeared when incubated with lucerne juice, and the extent was greater (P < 0.01) in XG than in GG. The disappearance of GG was increased (P < 0.01) when ensilage was fortified with added glucose, while that of XG was unaffected with or without the fermentable substrate. Rumen fermentation had little impact on GG and XG, whereas a portion of MRPs disappeared when microbial activity was enhanced by adding lucerne hay to the media. Volatile fatty acid production was unaffected by MRPs in either ensilage or rumen fermentation. These results suggest that the effect on MRPs of anaerobic fermentation may be different between ensilage and rumen digestion. Significant amounts of MRPs would enter the intestine when ruminants are fed hay‐based diets rather than silage‐based diets. © 2000 Society of Chemical Industry